Production of breathing composite sheet

Abstract

Breathing composite sheet can be produced from a thermoplastic resin and a porous substrate, such as a non-woven fabric sheet, by extrusion-laminating technique using a specified cooling roll, the surface of which has been at least partly modified with a covering material having specified ranges of thermal conductivity and hardness properties. The extruded molten thermoplastic film carried on the porous substrate is effectively perforated at the modified surface of the cooling roll so as to give a breathing composite sheet.

What is claimed is: 
     
       1. A method for preparing a breathing composite sheet from a thermoplastic resin and a porous substrate by extrusion-laminating technique, wherein a modified roll having a smooth surface is employed to perforate an extruded molten thermoplastic film which has just been extruded onto the porous substrate, at least part of the surface of the roll with which the extruded molten thermoplastic film is brought into direct contact being formed of a material having a thermal conductivity within the range of from 0.03 kcal/m·hr·°C. to 5 kcal/m·hr·°C. and a hardness of not less than HDA 60 as measured in accordance with the method of JIS K7215. 
     
     
       2. A method as claimed in claim 1 wherein the proportion of the total surface area formed from said material to the whole surface area of the roll is not less than 0.05%. 
     
     
       3. A method as claimed in claim 1 wherein the product composite sheet is of a three-layer structure comprising a core layer of said porous substrate and two outer layers of said thermoplastic resin, wherein the two outer layers of said thermoplastic resin are perforated. 
     
     
       4. A method as claimed in claim 2 wherein the product composite sheet is of a three-layer structure comprising a core layer of said porous substrate and two outer layers of said thermoplastic resin, wherein the two outer layers of said thermoplastic resin are perforated.